This ship was a passenger ferry, which I assume travels a short distance, stops at the dock, and then goes back. While at the dock, batteries could be recharged.
I guess...but I did actually hear of a cruise ship with that garbage.
Anyway, I guess the people who build ships need to learn the SAME LESSON that everyone learns the hard way, which is that Lithium Batteries are not toys and are not forgiving. They were just very lucky not to fry a boatload of people.